It is desirable for certain applications to combine the AC current from two AC single phase power sources having about the same voltage to drive an AC load. In particular, many pleasure boats have single phase AC load requirements of about 240 volts and 100 amperes. Typically, marinas where such pleasure boats land have single phase AC power sources cable of delivering 240 volts and only 50 amperes. A prior art system enables such boats to be powered by marinas having AC power sources which are combined to satisfy the boat power requirements. The AC commercial system includes a controller employing a considerable number of relays which frequently do not respond in sufficient time to provide safe and proper operation of the pleasure boat electrical system and is often out of service due to moisture in the relays and in the connections between the relays.